Limiting Hardness of Polymer/Ceramic Composites

Abstract

The main deficiency of proprietary composite materials for esthetic restoration of teeth is that they are much less resistant to wear than enamel. Many factors are involved in such a complex service property as some simpler related property. Limiting attention to static mechanical properties, it is to be noted that the proprietary composite materials are not inferior to enamel in respect of compression strength and tensile strength. On the other hand, it is well known that they are much softer, generally having a Knoop hardness number less than 60 Kg/mm2 whereas values near 380 have been reported for enamel (1,2). An obvious reason for this difference is that enamel contains a much greater ceramic content (95 wt-%) than most proprietary materials (60–80 wt-%). This might be rationalized in relation to wear by supposing that closely packed ceramic particles behave cooperatively and cannot be dislodged as easily from the surface as isolated particles. The objective of the present work is to find how hardness depends on the loading of ceramic particles in a polymeric matrix.